4 o SCIENCE PROGRESS. 



more fully in Kiihne's second paper. There are not only 

 differences in solubility, but differences in elementary com- 

 position, differences in behaviour to such reagents as 

 metaphosphoric and trichloracetic acids ; and peptone when 

 dry stands alone among the products of proteolysis, by 

 hissing like phosphoric anhydide does on the addition of 

 water. 



Chittenden takes up the matter from rather a different 

 point of view. He has considered it necessary to repeat 

 his old experiments with as pure a specimen of proteid as 

 he has been able to obtain, instead of using white of egg or 

 other similarly impure raw materials. The proteid he has 

 selected is the crystallised globulin or vitellin from hemp 

 seed. He also entirely disagrees with Pekelharing, as 

 under these more stringent conditions he confirms his older 

 work ; he, however, makes out a few new points, and so a 

 brief resumd of the entire paper may not be unprofitable. 



He performed two separate digestions on a large scale, 

 one of which was continued for three, the other lor ten 

 days. The products of digestion were carefully separated 

 from one another and analysed ; their reactions are ex- 

 haustively described, including their specific rotatory power. 

 In separating proteoses from peptone the difficulties of 

 manipulation are recognised, and so far as is at present 

 possible obviated. The investigation, however, lends no 

 support to Pekelharing's views, but is in complete accord- 

 ance with Kuhne's contention that peptone is a definite, 

 well-characterised substance. Its amount increases, and 

 that of proteose diminishes as digestion progresses, but an 

 artificial digestion in which all proteose is converted into 

 peptone has not yet been obtained. The progressive 

 changes from primary proteose to deutero-proteose and 

 peptone are most marked in the early stages of digestion ; 

 the disappearance of deutero-proteose and the formation of 

 peptone is subsequently a very gradual process. 



In the proteolytic process, at least four products of 

 hydration and cleavage are easily recognisable, namely, 

 proto-proteose, hetero-proteose, deutero-proteose and pep- 

 tone. The examination of the percentage composition of 



